Mechanical impedance tuners use probes to simulate impedance values for various microwave and RF measurements such as load pull or source pull measurements or noise parameter measurements. The transmission line of the tuner may be a slab line. A slab line is a type of transmission line having opposed parallel slabs (or plates) with a center conductor between them. The slabs act as the outer conductor of the transmission line. The probes are movable in a direction transverse to the center conductor of the transmission line of the tuner, and also in a direction along the center conductor. As the probe moves closer to the center conductor, the impedance mismatch increases, while the mismatch decreases as the probe is moved away from the center conductor. The probes can generate high reflections and act to transform the characteristic impedance of the slab line to other impedance values. A major shortcoming is, as is known to microwave engineers, the narrow band of these probes.
Commonly owned U.S. Pat. No. 7,589,601 describes multi-section probes, in which the sections are separated by gaps.